Vehicle navigation system with improved powerup performance

ABSTRACT

A navigation system includes a driver presence sensor and engine running detection circuitry. When the detection circuitry determines that the engine of the vehicle is not running, the navigation system enters a low power mode. When the presence of the driver is detected, the navigation system begins power up, switching from a low power to a full power operational mode. If the detection circuitry does not determine that the engine is running within a predetermined time period, the navigation system reenters the low power mode. The detection circuitry monitors the vehicle&#39;s electrical system and determines that the engine is running when an AC content exceeds a predetermined threshold.

This application is a Divisional of Ser. No. 09/060,899, filed Apr. 15,1998.

BACKGROUND OF THE INVENTION

The present invention relate generally to vehicle navigation systems andmore particularly to a vehicle navigation system with improved startupperformance.

Known vehicle navigation systems generally include a plurality of motionand position determining devices, such as a GPS receiver,accelerometers, gyros, wheel speed sensors, etc. The navigation systemfurther includes a CPU receiving data from all of the sensors and havinga hard drive containing a database of roads which may be traveled by thevehicle. As is generally known, the navigation system determines theposition of the vehicle relative to the database of roads and displaysthe current position of the vehicle on a display. Further, the drivercan select a destination relative to the database of roads. Thenavigation system then displays turn-by-turn instructions to the driverto guide the driver to the selected destination.

In order to conserve battery power, navigation systems generally enter a"low power" mode when the vehicle engine is not running. In low powermode, the hard drive is not spinning, the CPU is not booted, the sensorsdo not consume power and the GPS receiver does not receive GPS signals.To determine whether the engine is running, the current systems areconnected to the "ON" position of the vehicle ignition switch. When theignition switch is turned to the ON position, the navigation systemswitches from low power mode to full power mode. At that time, the harddrive in the navigation system starts spinning, the CPU is booted, themotion sensors begin to warmup and stabilize, and the GPS receiverreceives GPS signals and begins calculating a GPS position solution.This "warmup" period by the navigation system components requires timeduring which the driver of the vehicle may be taking other actions thatthe navigation system needs to monitor in order to know the currentposition of the vehicle. It would be difficult and undesirable to forcethe vehicle to remain still while the navigation system is in the warmupperiod. In cold weather, this warmup period could be 30 seconds or more.

Additionally, startup performance of the navigation system is closelyrelated to the GPS receiver's "time to first fix." To minimize thistime, it is important for the GPS receiver to have fresh satelliteephemeris data. This data, which is used to determine the preciselocation of the GPS satellites, typically needs to be refreshed at leastevery four hours. If the vehicle is parked for more than four hours, theGPS receiver must first obtain fresh ephemeris data before calculatingan accurate position solution. This further delays the startupperformance of the vehicle navigation system.

SUMMARY OF THE INVENTION

The present invention provides a vehicle navigation system havingimproved powerup performance. The vehicle navigation system includes asensor for detecting the presence of the driver, such as a motionsensor. When the sensor determines that the driver is present, thenavigation system enters the warmup period, switching from low powermode to full power mode. The hard drive starts spinning, the CPU isbooted, the sensors begin warmup and the GPS receiver and CPU begincalculating a GPS position solution. By the time the driver enters thevehicle and starts the car, the navigation system is operational.

If the presence of the driver is detected, but the vehicle engine is notrunning within a predetermined time period, the navigation systemreturns to the low power mode. This reduces power consumption in theevent of a false detection of the driver's presence, or if the driverdid not start the vehicle.

The vehicle navigation system can monitor the ignition switch of thevehicle to determine if the engine is running within the time period;however, preferably the vehicle navigation system includes enginerunning detection circuitry which simply monitors the power supply fromthe vehicle to the vehicle navigation system. The engine runningdetection circuitry monitors the electrical power supply of the vehicle.When the engine is not running, the voltage of the vehicle power supplyis a fairly constant DC voltage, typically 12 to 14 volts. When theengine is running, there is a measurable AC voltage superimposed on theDC power supply output. The AC voltage is a result of transientsgenerated by the ignition system primary circuit and charge of pulsesfrom the generator/alternator.

Generally, the engine running detection circuitry monitors the amplitudeof the AC content. The engine running detection circuitry may use bothtime and frequency domain techniques to monitor the AC content in thevehicle power supply. When the AC content exceed a predeterminedthreshold, the engine running detection circuitry determines that theengine is running. When the AC content falls below the predeterminedthreshold, the engine running detection circuitry determines that theengine is not running. If the engine running detection circuitrydetermines that the engine is not running within a predetermined timeperiod after the presence of the driver has been detected, thenavigation system reenters the low power standby mode. While the engineis running, the navigation system continues to operate at full power.When the engine running detection circuitry determines that the engineis not running for a predetermined time period, the navigation systementers the low power standby mode.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages of the present invention will be readily appreciated asthe same becomes better understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a schematic of the navigation system of the present inventioninstalled in the vehicle;

FIG. 2 is a lower level schematic of the navigation system of FIG. 1;

FIG. 3 is a detailed schematic of the conditioning circuitry of FIG. 2;and

FIG. 4 is a high-level state diagram of the operation of the navigationsystem of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The navigation system 20 of the present invention is shown schematicallyin FIG. 1. The navigation system 20 includes a CPU 22 connected to adisplay 24, such as a high resolution LCD or flat panel display. The CPU22 is also connected to an input device 26 such as a mouse, keyboard,key pad or remote device. Alternatively, the display 24 can be a touchscreen display. The navigation system 20 further includes a storagedevice 28, such as a hard drive 28 or CD ROM, connected to the CPU 22.The storage device 28 contains a database including a map of all theroads in the area to be traveled by the vehicle 32 and may contain thesoftware for the CPU 22, including the graphical user interface, routeguidance, operating system, position-determining software, etc.

The navigation system 20 preferably includes position and motiondetermining devices, such as a GPS receiver 34, a gyroscope 36, acompass 38, a wheel speed sensor 40 and an orthogonal multiple axisaccelerometer 41 all connected to the CPU 22 (connections not shown forsimplicity). Such position and motion determining devices are well knownand are commercially available. A vehicle security system 42, preferablyincluding a remote entry system having a remote 44, is installed in thevehicle 32. Generally, the components described above are powered by thevehicle's electrical system, which preferably includes the vehiclebattery 48. The navigation system 20 further includes detectioncircuitry 50 connected to the vehicle's electrical system or battery 48and sending a signal to the CPU 22. Although the detection circuitry 50is shown as a separate component, it could be located on the CPU 22.

The navigation system 20 determines the position of the vehicle 32relative to the database of roads utilizing the position and motiondetermining devices. The driver selects a destination relative to thedatabase of roads utilizing the user input device 26 and the display 24.The navigation system 20 then displays turn-by-turn instructions to thedriver to guide the driver to the desired destination from the presentposition.

FIG. 2 is a lower level schematic of the navigation system 20 of thepresent invention. As can be seen in FIG. 2, the detection circuitry 50generally comprises conditioning circuitry 52, which will be describedin more detail below, an analog to digital converter 54 and amicrocontroller 56, preferably a Microchip PIC12C671 or PIC12C672. Thedetection circuitry 50 monitors the voltage on the vehicle electricalsystem or battery 48. Because the vehicle's electrical system or battery48 will typically be around 12 to 14 volts DC, the conditioningcircuitry 52 filters out the DC component of the power signal from thebattery 48 and shifts the voltage to the middle of the range of inputsof the analog to digital converter 54. The microcontroller 56periodically samples the output from the analog to digital converter 54to measure the AC content of the power supply signal from the battery48. Preferably, the microcontroller 56 samples the output from theanalog to digital converter 54 every millisecond.

The microcontroller 56 preferably compares the largest peak to peakvoltage variation over a one second interval to a predeterminedthreshold, such as 100 to 300 millivolts. The specific threshold maydepend upon the specific vehicle into which the navigation system 20 isinstalled. Further, the microcontroller 56 may also perform a Fourier orwavelet transform on the sampled AC content and look for signal contentat certain frequencies to determine whether the engine is running. Againthe spectral analysis of the signal may depend upon the specific vehicleinto which the navigation system 20 is installed. Those skilled in theart would be able to adapt the detection circuitry 50 to a specificvehicle by observing the AC content while the engine is running versusnot running.

If the detection circuitry determines that the AC content of the powersupply signal indicates that the engine is running, the microcontroller56 generates an engine running signal, indicating that the engine isrunning. If the AC content of the power supply signal does not exceedthe predetermined threshold, the detection circuitry 50 determines thatthe vehicle engine is not running, and does not generate an enginerunning signal.

The detection circuitry 50 may also monitor the vehicle power supply todetermine the presence of the driver. When the doors are unlocked usinga keyless entry fob, the automatic door lock actuators will generate atransient on the vehicle electrical system that the detection circuitry50 will detect as a short duration AC signal. Moreover, when the door isopened and the interior lights are turned on, a transient will begenerated on the vehicle electrical system which the detection circuitrycan recognize. In either event, the detection circuitry 50 determinesthe presence of the driver approaching or entering the vehicle 32.

The detection circuitry 50 may alternatively receive a signal from thevehicle security system 42 indicating the presence of the driver in ornear the vehicle 32. This signal may be generated by a sensor 60 whichis part of the vehicle security system 42. As is generally known invehicle security systems, the sensor 60 may comprise a motion sensor,door pin switches, vibration sensor, noise sensor, or other sensorsknown in the vehicle security art. Additionally, or alternatively, thepresence of the driver may be indicated by the remote entry sensor 62,which may also be integrated with the vehicle security system 42. As isgenerally known, the remote entry sensor 62 receives an RF or infraredsignal from the remote entry remote 44, which is typically carried bythe driver. Alternatively, the presence of the driver may be detected bythe accelerometer 41 which is part of the navigation system 20.

When the presence of the driver is detected by the detection circuitry50, either by monitoring the AC content or the vehicle security system42, the detection circuitry 50 selectively sends a warmup signal to theCPU 22 which may be relayed to the other electrical components 24, 34,36, 38, 40, 28. Alternatively, as shown in phantom, the detectioncircuitry 50 can send the warmup signal directly to each of thecomponents, indicated collectively as components 66.

The conditioning circuitry is shown in more detail in FIG. 3. Theconditioning circuitry 52 receives the power supply signal at input 72and filters out the DC and lower frequency components with capacitor 74and resistor 76. Capacitor 74 is preferably 0.1 microfarads to 0.2microfarads. Resistor 76 is preferably 100 Ohms. This places the ACcontent of the power supply signal at a voltage divider circuit, whichcomprises two 100 k Ohm resistors 78 connected to a 3.3 volt powersupply. This places the AC content of the power supply signal in themiddle of the range of the analog to digital converter 54 and providesthe maximum available peak to peak input voltage swing. A diode 80 maybe coupled to the output 82.

The operation of the vehicle navigation system 20 will be described byreferring to FIG. 2 and a state diagram shown in FIG. 4. When thevehicle engine is not running, the vehicle power supply or battery 48provides a fairly constant DC voltage, preferably 12 to 14 volts. The DCcomponent of the power supply signal is filtered out by the conditioningcircuitry 52 and the peak to peak AC content of the power supply signaldoes not exceed the predetermined threshold. Therefore, themicrocontroller 56 in the detection circuitry 50 determines that vehicleengine is not running, and so indicates to the CPU 22 and otherelectrical components 24, 28, 34, 36, 38 and 40. These electricalcomponents then enter a low power mode in state 90 to conserve power. Aswill be recognized, some of these electrical components require somepower even in low power mode.

Periodically, (preferably approximately every second) themicrocontroller 56 exits low power mode (state 90) and checks whetherthe engine is running. If the detection circuitry 50 detects that theengine is running, even if the presence of the driver has not beendetected, the detection circuitry 50 indicates to the CPU 22 and otherelectrical components to switch to fall power in state 96.

Preferably, the CPU 22 and GPS receiver 34 also switch on briefly everyfour hours in state 93. In state 93, the GPS receiver 34 collects andstores fresh ephemeris data. The CPU 22 and GPS receiver 34 then reenterlow power mode in state 90 for up to four more hours. If the GPSreceiver 34 is unable to receive a satellite signal and obtain freshephemeris data within a predetermined time period (approximately 90seconds), the CPU 22 and GPS receiver 34 reenter low power mode in state90. If the GPS receiver 34 is unable to receive a satellite signal afterseveral tries (such as three or four), the microcontroller 56 does notenter state 93 for additional attempts until after the engine isstarted. This would indicate that the vehicle 32 may be parked for along period in a parking structure or at some location where satellitesignals cannot be received. The GPS receiver 34 preferably also collectsand stores fresh almanac data periodically as well, although it need notbe gathered as often, such as once per week.

When the driver approaches the vehicle and activates the remote entryremote 44, the detection circuitry 50 detects the transient generated bythe door lock actuators on the vehicle electrical system and generates awarmup signal, which is sent to the CPU 22 and the other electricalcomponents. In state 94, the presence of the driver is detected and theCPU 22 boots up and starts the hard drive spinning 28. The otherelectrical components begin their warmup period as well. The display 24switches to a full power mode and warms up in a few seconds. The GPSreceiver 34 receives signals from the GPS satellite and may begincalculating a GPS position solution. The other sensors, such as thegyroscope 36, compass 38, and wheel speed sensor 40 begin their warmupperiod as well, switching to full power. The navigation system 20 isfully operational and can monitor the initial actions taken by thedriver by the time the driver enters the vehicle and starts the engine.

When the driver starts the engine, the detection circuitry 50 detectsthe AC content in the vehicle electrical system or battery 48 and thenavigation system 20 enters state 96. The AC content is a result oftransients generated by the ignition system primary circuit and chargepulses from the generator/alternator. When a peak to peak voltageexceeding the predetermined threshold, such as 200 millivolts, isdetected by the microcontroller 56, the detection circuitry 50determines that the engine is running and the navigation system 20remains at full power. If the detection circuitry 50 determines that theengine is not running within a predetermined time period of detectingthe presence of the driver, preferably 30 to 90 seconds, the detectioncircuitry 50 generates a signal to the CPU 22 and other electricalcomponents to reenter low power mode in state 90. If the detectioncircuitry 50 determines that the vehicle 32 is still occupied (such asby monitoring the accelerometer 41) even though the engine is notrunning, the navigation system 20 preferably remains at full power forsome extended predetermined time period.

The navigation system 20 of the present invention has improved power upperformance. The navigation system 20 is powered up earlier, byanticipating its use by sensing the presence of the driver. Thenavigation system 20 further includes improved detection circuitry 50for determining whether the engine is running. The detection circuitry50 for the presence of the driver and the running engine simply monitorsthe power supply, without the need to connect an extra wire to theignition switch. Further, the navigation system 20 maintains freshephemeris data by periodically exiting sleep mode to receive a satellitesignal. The improved navigation system 20 will determine the presentposition of the vehicle 32 and monitor the initial actions taken by adriver of the vehicle 32 after the engine is started.

In accordance with the provisions of the patent statutes andjurisprudence, exemplary configurations described above are consideredto represent a preferred embodiment of the invention. However, it shouldbe noted that the invention can be practiced otherwise than asspecifically illustrated and described without departing from its spiritor scope.

What is claimed is:
 1. A method for operating a vehicle navigationsystem including the steps of:a) placing the navigation system in a lowpower mode while an engine of the vehicle is not running; b) monitoringan AC component of a power supply of the vehicle while the navigationsystem is in the low power mode; c) determining whether the engine isrunning based upon said step b); and d) switching the navigation systemfrom the low power mode to an operating mode based upon a determinationin said step c) that the vehicle engine is running.
 2. The method ofclaim 1 wherein said step c) includes the step of comparing the ACcomponent to a predetermined value.
 3. The method of claim 1 furtherincluding the step of switching the navigation system to said low powermode based upon detecting that said engine is not running after saidstep d).
 4. The method of claim 1 further including the steps of:e)detecting that the engine of the vehicle is not running after said stepd); and f) returning the navigation system to the low power mode if theengine is not running within a predetermined time period after said stepe).
 5. The method of claim 4 further including the steps of:detectingthe presence of a driver in the vehicle; and remaining in said fullpower mode after the predetermined time period based upon the detectionof the presence of the driver in the vehicle.
 6. The method of claim 1wherein said step d) further includes the step of starting a hard drive.7. The method of claim 1 further including the step of calculating aposition of the navigation system after said step d).
 8. The method ofclaim 7 further including the step of receiving a GPS signal after saidstep d).
 9. A method for operating a vehicle navigation system includingthe steps of:a) maintaining the navigation system in a low power modewhile an engine of the vehicle is not running; b) monitoring a powersupply of the vehicle; c) determining whether the engine of the vehicleis running based upon said step b); and d) switching the navigationsystem from the low power mode to a full power mode based upon adetermination in said step c) that the vehicle engine is running. 10.The method of claim 9 further including the step of:e) filtering asignal from the power supply before said step b).
 11. The method ofclaim 9 wherein said step b) includes the step of monitoring an accomponent of a signal from the power supply and said step c) includesthe step of determining whether the engine of the vehicle is runningbased upon said monitoring an ac component.
 12. The method of claim 9wherein said step d) further includes the step of starting a hard drive.13. The method of claim 9 further including the steps of:e) detectingthat the engine of the vehicle is not running after said step d); and f)returning the navigation system to the low power mode if the engine isnot running within a predetermined time period after said step e). 14.The method of claim 9 further including the step of calculating aposition of the navigation system after said step d).
 15. The method ofclaim 14 further including the step of receiving a GPS signal after saidstep d).
 16. The method of claim 13 further including the stepsof:detecting the presence of a driver in the vehicle; and remaining insaid full power mode after the predetermined time period based upon thedetection of the presence of the driver in the vehicle.
 17. The methodof claim 9 wherein said step b) includes the step of monitoring an ACcomponent of a signal from the power supply and said step c) includesthe step of comparing the AC component to a predetermined value.
 18. Themethod of claim 9 further including the step of switching the navigationsystem to said low power mode based upon detecting that said engine isnot running after said step d).